Eliciting T Cell mediated immune responses is a very promising objective for the development of novel therapies for the treatment of HIV infection. Preliminary results obtained through collaboration of the Project Leaders of this Program provided new, unexpected optimism that the induction of viral control might be achievable long after initial retroviral infection. However, development and testing of immune therapies for HIV will require versatile and efficient tools in order to best evaluate those responses or predict immune control. This project intends to address this unmet need. We will study a new assay (VIR assay) designed to overcome the logistical and technical barriers of its predecessors that have limited their use in the diagnostic clinical setting. A key feature of the assay is that all cells and all viral antigens involved in an immune response are represented. The assay allows us to monitor the quantity of virus specific T cells quickly and easily, it can be applied to every patient, and it can be performed from the same specimen submitted for CD4-CD8 count because it requires only a few milliliters of blood and FACS analysis after overnight antigenic activation. The preliminary results of the VIR assay are very encouraging, in that they correlated with viral control during treatment interruptions in both acutely and chronically infected patients, as well as in a non-human primate model. Other traditional assays, such as the recombinant vaccinia- and the peptide-based assays allow a better resolution of the breadth of the immune response. These tests will be compared to and used in conjunction with the VIR assay to identify correlates of immune control. This battery of well-characterized and clinically tested assays will assist investigators (including those in the other Projects of this Program) in monitoring treatment interruptions, immune based therapies, and therapeutic immunization and, ultimately, to better optimize treatment schedules on an individual basis. Aim 1 of this Project intends to better understand and further optimize the VIR assay by performing simultaneous analysis of HIV-specific T cell subtypes Aim 2 intends to compare the VIR assay, the recombinant vaccinia based assay, and the peptide based assay to identify correlates of immune control Aim 3 intends to use the same assays in different clinical and pre-clinical settings in order to test the efficacy of therapeutic vaccines